The conversion of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) to mevalonate is an early and rate-limiting step in the cholesterol biosynthetic pathway. This step is catalyzed by the enzyme HMG-CoA reductase. Statins inhibit HMG-CoA reductase from catalyzing this conversion. As such, statins are collectively potent lipid lowering agents.
Atorvastatin calcium is currently sold as Lipitor® having the chemical name [R-(R*,R*)]-2-(4-fluorophenyl)-β,δ-dihydroxy-5-(1-methylethyl)-3-phenyl-4-[(phenylamino)carbonyl]-1H-pyrrole-1-heptanoic acid calcium salt (2:1) trihydrate and the formula:

The nonproprietary name designated by USAN (United States Adopted Names) is atorvastatin calcium and by INN (International Nonproprietary Name) is atorvastatin. Under the established guiding principles of USAN, the salt is included in the name whereas under INN guidelines, a salt description is not included in the name.
Atovastatin calcium is a selective, competitive inhibitor of HMG-CoA reductase. As such, atorvastatin calcium is a potent lipid lowering compound and is thus useful as a hypolipidemic and/or hypocholesterolemic agent, as well as in the treatment of osteoporosis, benign prostatic hyperplasia, and Alzheimer's disease.
A number of patents have issued disclosing atorvastatin calcium, formulations of atorvastatin calcium, as well as processes and key intermediates for preparing atorvastatin calcium. These include: U.S. Pat. Nos. 4,681,893; 5,273,995; 5,003,080; 5,097,045; 5,103,024; 5,124,482; 5,149,837; 5,155,251; 5,216,174; 5,245,047; 5,248,793; 5,280,126; 5,397,792; 5,342,952; 5,298,627; 5,446,054; 5,470,981; 5,489,690; 5,489,691; 5,510,488; 5,686,104; 5,998,633; 6,087,511; 6,126,971; 6,433,213; and 6,476,235, which are herein incorporated by reference.
Atorvastatin calcium can exist in crystalline, liquid-crystalline, non-crystalline and amorphous forms.
Crystalline forms of atorvastatin calcium are disclosed in U.S. Pat. Nos. 5,969,156, 6,121,461, and 6,605,729 which are herein incorporated by reference.
Additionally, a number of published International Patent Applications have disclosed crystalline forms of atorvastatin calcium, as well as processes for preparing amorphous atorvastatin calcium. These include: WO 00/71116; WO 01/28999; WO 01/36384; WO 01/42209; WO 02/41834; WO 02/43667; WO 02/43732; WO 02/051804; WO 02/057228; WO 02/057229; WO 02/057274; WO 02/059087; WO 02/072073; WO 02/083637; WO 02/083638; and WO 02/089788.
Atorvastatin is prepared as its calcium salt, i.e., [R-(R*,R*)]-2-(4-fluorophenyl)-β,δ-dihydroxy-5-(1-methylethyl)-3-phenyl-4-[(phenylamino)carbonyl]-1H-pyrrole-1-1-heptanoic acid calcium salt (2:1). The calcium salt is desirable since it enables atorvastatin to be conveniently formulated in, for example, tablets, capsules, lozenges, powders, and the like for oral administration.
U.S. Pat. No. 5,273,995 discloses the mono-sodium, mono-potassium, hemi-calcium, N-methylglucamine, hemi-magnesium, hemi-zinc, and the 1-deoxy-1-(methylamino)-D-glucitol (N-methylglucamine) salts of atorvastatin.
Also, atorvastatin free acid, disclosed in U.S. Pat. No. 5,273,995, can be used to prepare these salts of atorvastatin.
Additionally, U.S. Pat. No. 6,583,295 B1 discloses a series of amine salts of HMG-CoA reductase inhibitors which are used in a process for isolation and/or purification of these HMG-CoA reductase. The tertiary butylamine and dicyclohexylamine salts of atorvastatin are disclosed.
We have now surprisingly and unexpectedly found novel salt forms of atorvastatin including salts with ammonium, benethamine, benzathine, dibenzylamine, diethylamine, L-lysine, morpholine, olamine, piperazine, and 2-amino-2-methylpropan-1-ol which have desirable properties. Additionally, we have surprisingly and unexpectedly found novel crystalline forms of atorvastatin which include salts with erbumine and sodium which have desirable properties. As such, these salt forms are pharmaceutically acceptable and can be used to prepare pharmaceutical formulations. Thus, the present invention provides basic salts of atorvastatin that are pure, have good stability, and have advantageous formulation properties compared to prior salt forms of atorvastatin.